The reviewers at Photozone appear not to have fully accepted that post capture lens corrections are now a normal part of the image making process.

Normal according to whom? Not all lenses require as much software correction as others. Some require very little. Some require much more.

So they RAW convert with RAW Therapee, demonstrate 5.8% barrel distortion at 12mm and decry that as "excessive".

It is pretty excessive for a $1300 lens.

But if, like the rest of us, you simply use the camera as designed and allow the distortion to be corrected automatically in camera then all you will see is a mild amount of residual distortion. In addition the Photozone reviewers say that the automatic distortion correction is "lossy" , however those of us who have actually used the lens for several thousand photos, often critically inspected for sharpness, are unaware of this supposed lossiness.

Whether you have noticed it or not, correction is, in fact, a lossy operation. There is nothing 'supposed' about that statement, and the Photozone reviewers are 100% correct.

They also criticise corner shading which is present but which I hardly ever notice in actual photos and if I do, it is easily removed in a RAW converter.

Relying again on software correction for a problem that should probably be optically corrected in a premium lens.

In other words they are complaining about lens attributes which are of no concern in the real world.

Not true. The attributes are of concern, which is why you must apply software correction in order to fix them. The point is, at what price should we expect a lens to be optically excellent? It costs less to build a lens with poor optics, then correct resulting problems in software.

As long as the manufacturers pass on some of the savings they realize from these cost-cutting measures, I think most are OK with the idea. If, however, a manufacturer builds a lens with poor optics and tries to sell it as a premium quality lens, there are plenty of discriminating buyers who won't appreciate the trick.

On what grounds do you leap to the conclusion that designing lenses to be software-corrected in one specific regard (geometric distortion) is done only or primarily for the purpose of cutting costs?

I never said what you're asking me to defend. Software correction is practically free, however.

And what makes you think that the end results (after correction) must necessarily be worse than they would have been for a lens corrected by optical means only?

I have also not made that claim.

I find no reason to think along such lines. If the end results, after correction, are good, as they are for those MFT lenses with strong barrel distortion prior to correction that I own and use (12/2, 7-14/4, 14-45/3.5-5.6), what's wrong with it?

Nothing is wrong with it if the end results are as good. I never claimed otherwise. As a matter of fact, I specifically said that most are probably fine with the idea if the cost-savings are shared with the consumer.

I think of this lens-design strategy as an asset rather than a liability for MFT and I am sure the main reason that some others refrain from taking advantage of it is that it runs into trouble with an optical viewfinder.

I don't have a problem with the strategy.

When you compose, you want to know what you will get once the image is properly corrected. Possible with an EVF, not possible with an OVF.

Interesting theory- sounds plausible.

If you have any links to good reading on the subject, I'd be happy to have a look. Might save you some effort trying to retype what you've already written elsewhere.